USPTO Patents Application 10808467

FP03-0408-00

TITLE OF THE INVENTION
DISTANCE. MEASURING DEVICE
BACKGROUND OF THE INVENTION
Field of the Invention
5 [0001] The present invention relates to a

distance measuring device ' that measures the
distance to an object to be measured, and more
particularly to an active type distance measuring
device suitably used for cameras or the like.

10 Related Background Art .

[0002] Conventionally, as an active type

distance measuring device used for cameras or the
like, the following distance' measuring device is
known. That is, beam of light is projected from

15 an infrared light emitting, diode (hereinafter,

referred to as ^^IRED'') to an object to be
measured, the reflected light of the projected
beam of light is received by a position sensitive
detector (hereinafter, referred to as ""PSD"') , and

20 the signal output from the PSD is calculated and

processed by signal processing circuit and
arithmetic circuit and output therefrom as
distance information; thereby the distance to the
object to be measured is detected by a CPU.

25 Further, in the case where the distance

measurement is made by only one light" projection.

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an error may be generated. Accordingly, it is
preferred that a distance measuring routine
including light projection with light projecting
means, light reception with light receiving means,
5 output of output signal with light receiving

means, and discharge or charge of an integration
capacitor, is carried out several times to obtain
plural pieces of distance information, and the
plural pieces of distance information are
10 integrated by an integration circuit at

predetermined intervals to be averaged. The
integration of the distance information with the
integration circuit is made by discharging the
integration capacitor; and from that state, a
15 voltage corresponding to the distance information

is applied to accumulate electric charge.
SUMMARY OF THE INVENTION

[00O3] According to the distance measuring

device as described above, the number of times of

20 repetition of the distance, measuring routine

• (hereinafter, referred to as "number of times of
distance measuring routine") is uniformly set up
in the following manner. That is, the number of
times of the distance measuring routine is

25 uniformly determined irrespective of the

difference in the integration current and the

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capacity of integration capacitor depending on
the individual product; and assuming an
individual product of which capacity of the
integration capacitor is the smallest and- the
5 integrated current is the largest in the

difference range, and in such individual product,
even when the amount of the accumulated charge is
the largest (object to be measured is close), the
■amount of the accumulated' charge does not exceed
10 the capacity- of the integration capacitor.

[0004] However, in the above distance

measuring device, since the number of times of
the distance measuring routine is uniformly
. determined, there may be a case that, when the
-15 capacity of the integration capacitor is large or

the integrated current is small due to . the
difference of the product, the integration
operation, in which the capacity of the
integration capacitor is fully used, can not be
20 made. Thus, satisfactory measuring accuracy is

not obtained.

[0005] Fig. 8 is a timing chart of

conventional distance measuring device in the
case where the distance measurement is made at
25 the closest distance capable of photographing for

a camera. The abscissa axis represents

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integration time; and the ordinate axis
represents voltage of the integration capacitor.
Conventionally/ the number of times of the
distance measuring routine is fixed irrespective
5 of the individual product- Therefore, as shown

in Fig. 8, in an individual product {distance
measuring device 1) o.f which capacity of the
integration capacitor is the smallest and the
integration current is the largest, electric

10 charge is accumulated until the voltage of the

integration capacitor reaches the substantially
maximum value; thus the range, of available AD
signal value can be used' effectively. However,
in the case of many average individual products

15 (distance measuring device 2) , since the

integration capacitor is not charged up to the
maximum voltage, satisfactory resolution of the
AD signal cannot be obtained; thus, accuracy of
the distance measurement cannot be obtained.

20 Further, in the individual product (distance

measuring device 3), of which capacity of the
integration capacitor is the largest and the
integration current " is the smallest, the
utilization rate of the capacity of the

25 integration capacitor and the range of the

available AD signal value become lowest.

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[0006] In order to solve the above problems,

a distance measuring device disclosed in Japanese
Unexamined Patent Application • Publication
(Tokukai) No. H5-280973 (Patent Document 1), it
5 is arranged so that elements, which change the

dynamic range such as the number of times of the
distance measuring routine^ integration time and
the capacity of the integration capacitor, are
controlled,

10 Patent Document 1: Japanese Unexamined Patent

Application Publication (Tokukai) No. H5-280973
[0007] However, in the above distance

measuring device, since it is arranged so that
elements are changed every, time of the distance

15 measurement,- • the operation to calculate the

distance becomes complicated and the measuring
time becomes long. When the distance measuring
time of the distance measuring device is long, in
the case that the distance measuring device is

20 used in a camera or the like, there are such

problems that an appropriate shutter chance can
not be obtained or the like.
• [0008] Accordingly, an object of the present

invention is to solve the above-described

25 problems and to provide a distance measuring

device capable of increasing the accuracy in the

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distance measurement without any complicated
distance measuring processing.

[0009] In order to solve the above-described

problems, a distance measuring device of the
5 present invention comprises light projecting

means for projecting beam of light onto an object
to be measured, light receiving means for
receiving reflected light of the beam of light
projected onto the object to be measured and

10 outputting output- signal corresponding to the

distance to the object to be measured,
integration means for discharging or charging an
integration capacitor corresponding to the output
signal ' to integrate the output signal, an AD

15 conversion means for AD converting the voltage of

the integration capacitor after predetermined
number of repeat of distance measuring routine
including light projection with the light
projecting means, light reception with the light

20 receiving means, outputting of output signal with

the light receiving means and discharging or
charging the integration capacitor, and detection
means for detecting the distance to the object to
be measured based on the AD converted conversion

25 signal, wherein the number of repeat of the

distance measuring routine is set saturating the

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integration capacitor through the repeat, when
the object to be measured is at a short range
alarm position.

[0010] According to the above-described

5 distance measuring device, since the number of

times. of the distance measuring routine is set up
in accordance with the differences such as the
integration current, the capacity of the
integration capacitor or the like in each product,

10 and thus, the value in which the voltage of the

integration capacitor at the short range alarm
position is saturated is obtained. Accordingly,
it is possible to carry out the integration
operation fully using the range of capacity of

15 the integration capacitor. Here, '^short range

alarm position" means a position determined as
the limit at the short range side where normal
photographing for a camera without misfocussing
is capable, and the camera is designed so that,

20 in the case where the object to be measured is in

a position nearer than that position, an alarm is
emitted and the photographing is not carried out.
In other words, ''short range alarm position" is
the nearest position that can be brought into a

25 • focal point by a camera to which the distance
measuring device is applied- Also, "integration

7

capacitor is saturated" means that, when the
output signal is charged to integrate/ the state
where the integration capacitor is fully charged
(the state where the integration capacitor has
reached saturation voltage level); and when
output signal is discharged to integrate, the
state where the integration capacitor voltage is
OV. In this case, not only the state where the
capacity is fully charged or completely OV, but
also, the following state is also included. That
is, the capacity is almost fully charged or
almost OV to an extent that the range of the
capacity of the integration capacitor is fully
us e d -

[0011] Further, the distance measuring device

in accordance with the present invention
comprises light projecting means for projecting
beam of light onto an object to be measured,
light receiving means for receiving reflected
light of the beam of light projected onto the
object to be measured and outputting output
signal corresponding . to the' distance to the
object to be measured, integration means for
discharging or charging an integration capacitor
corresponding to the output signal to integrate
the output signal, an AD conversion means for AD

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converting the voltage of the integration
capacitor after predetermined number of repeat of
distance measuring routine ' including light
projection with the light projecting means, light
5 reception with the light receiving means,

outputting of output signal with the light
receiving means and discharging or charging the
integration capacitor, and detection means for
detecting the distance" to the object to be

10 measured based on the AD converted conversion

signal, wherein the number of repeat of the
distance measuring routine is set saturating the
integration capacitor through the repeat, when
the object to be measured is at the distance

1.5 corresponding to the closest distance capable of

photographing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Fig. - 1 is a perspective view of the

front elevation of a camera in which a distance
20 measuring device in accordance with this

embodiment is used.

[0013] Fig. 2 is a perspective view of the

rear elevation of the camera in which the
distance measuring device in accordance with this
25 embodiment is used.

[0014] Fig, 3 is a diagram showing the

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configuration of a distance measuring device in
accordance with the eiubodiment •

[0015] Fig. 4 is a diagram showing the

circuit configuration of a first signal
5 processing circuit and an integration circuit in

the distance measuring device in accordance with
the embodiment.

[0016] Fig. 5 is a timing chart for

illustrating the operation of the distance
10 Q measuring device in accordance with the
embodiment . '

[0017] Fig. 6 is a flow chart for

illustrating the adjusting method of the distance
measuring device . in accordance with the
15 embodiment.

[0018] Fig-. 7 is a timing chart for

illustrating the opeiration of the distance
measuring . device in accordance with the
embodiment.

20 [0019] Fig. 8. is a timing chart for

illustrating the operation of a conventional
distance measuring device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] Hereinafter, embodiments in accordance

25 with the present invention will be described.

Identical elements will be given with identical

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reference numerals and letters, and redundant
descriptions will be oniitte.d.

[0021] Fig. 1 is a perspective view of the

front elevation of a camera 40 in which a
distance measuring device in accordance with this
embodiment is used. As shown in Fig. 1, the
camera 40 is equipped with a zoom lens barrel 41
provided' with a photographic lens for imaging an
object image on a silver film, an electric flash
light emitting window 43 from which electric
flash light is emitted, a yiewfinder window 45
through which a photographer checks an object, an
AF window (light projection) 47a in which an IRED
(infrared light emitting diode) for projecting
infrared ray onto the object is incorporated, an
AF window (light reception) 47b in which a PSD
(position sensitive detector) for receiving
reflected light from the object is incorporated,
a photometry window 49 in which a photometry
sensor for measuring the luminance of the object
is incorporated, and a shutter button 51 which
the photographer operates to give instruction of
shutter release, and so on.

[0022] Fig. 2 is a perspective view of the

rear elevation of the camera 40. As shown in Fig.
2, the camera 40 is equipped with an LCD display

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panel 53 that displays a selected photographing
mode or the like and date information or the like,
a flash button 55 for setting light emitting mode
of electric flash, a self timer button 56 for
setting the mode of self timer, a date button 57
for setting date and time, and a zoom button 58
to instruct the photographing angle in the wide
scope direction or the telescope direction.
[0023] Fig. 3 is a diagram showing the

configuration of the distance measuring device in
accordance with the embodiment. As shown in Fig.
3, the distance measuring , device 100 in
accordance with the embodiment is provided with a
CPU 1. The CPU 1 controls the entire camera,
which is equipped with the distance measuring,
device 100. The CPU 1 controls the entire camera
including the distance measuring device 100 based
on the program and parameter which are previously
stored in an EEPROM 2.

[0024] The distance measuring device 100 is

provided with an IRED (infrared light' emitting
diode) 4. The IRED 4 serves as light projecting
means that emits light and thereby projects
projection beam onto an object to be measured.
The IRED 4 is connected to the CPU 1 through a
driver 3 and its light emission is controlled by

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the CPU 1-

[0025] The driver 3 receives power supply

from a battery (not shown), which is included in
the camera, and supplies the power to, in
addition to the IRED 4, component parts of the
camera such as AFIC 10 according to the control
signal of the CPU 1; and for example, a driver IC
is used therefor.

[0026] Further, the distance measuring device

100 is provided with a PSD (position sensitive
detector) 5, The PSD 5 serves as light receiving
means for receiving each reflected beam of the
projection beam, which is projected onto the
object to be measured from each IRED 4.
[0027] Furthermore, the distance measuring

device 100 is provided with an auto-focusing IC
(hereinafter, referred to as ^^AFIC") 10. The
AFIC 10 serves as signal processing means for
processing the output signal from the PSD 5. The
operation of the AFIC 10 is controlled by the CPU
1; and the AF signal (integration signal) output
from the AFIC 10 is input to the CPU 1,
[0028] When projection beam of infrared light

is emitted from the IRED 4, the projection beam
is projected onto the object to be measured
through a projection lens (not shown) disposed in

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front of the IRED 4. A portion of the projection
beam is reflected/ and is received at any point
on the light receiving plane of the PSD 5 through
the light receiving • lens (not shown) disposed in
front of the PSD 5. The light receiving position
corresponds to the distance to the object to be
measured. The PSD 5 outputs two signals Ii and I2
corresponding to the light . receiving position*
[0029] The signal Ii is . a short-range side

signal, in which, if the received light amount is
at a fixed level/ the closer distance results in
the. larger value; the signal I2 is a long-range
side signal, in which, if the received light
amount is at a fixed level, the longer distance
results in the larger value. The sum of the
signals Ii. and I2 represents the amount of the
reflected light received by the PSD 5. The
short-range side signal Ii is input to the PSDN
terminal ' of the AFIC 10; the long-range side
signal I2 is input to the PSDF terminal of the
AFIC 10. However, practically, each signal of
the short-range side signal Ii and the long-range
side signal I2 with component of ambient light lo
depending on the external conditions, is input to
the AFIC 10.

[0030] The AFIC 10 is an integrated circuit

14

(IC) and comprises a first signal processing
circuit 11, a second signal processing circuit 12,
an arithmetic circuit 14 and an output circuit 15.
[0031] The first signal processing circuit 11

receives the input, which is the signal Ii+Io
output from the PSD 5, and after removing the
component of the ambient light lo included in the
signal, outputs the short-range side signal Ii.
Also, the second signal processing circuit 12
receives the input, which is the signal I2+I0
output from the PSD 5, and after removing- the
component of the ambient light lo included in the
signal, outputs the long-range side signal I2.
[0032] The aritlametic circuit 14 receives the

input of the short-range side signal Ii, which is
•output from the first signal processing circuit 11,
and the long-range side signal I2, which is output
from the second signal processing circuit 12, and
after operating the output ratio (Ii/(Ii+l2))/ outputs
an output ratio signal representing the result. The
output ratio (Ii/ (IiH-Ig) ) represents the light
receiving position on the light receiving plane of
the PSD 5; i.e., the distance to the object to be
measured.

[0033] The output circuit 15 receives the

input of the output ratio signal and integrates

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the output ratio multiple times along with the
integration capacitor 6^ which is connected to
the CINT terminal of the AFIC 10; thereby the S/N
. ratio is improved. Here, the integration of the
5 output ratio into the integration capacitor 6 is

performed in such manner that the integration
capacitor 6 in a discharged- state is gradually
charged corresponding to the output ratio signal-
[0034] Then, the integrated output ratio is

10-. output from the SOUT terminal of the AFIC 10 as

AF signal (integration signal). The CPU 1

receives the input of the AF signal output from
the AFIC 10, and after performing a predetermined
calculation to convert the AF signal into a

15 distance signal, sends the distance signal to a

lens drive circuit 7. The lens drive circuit 7
makes a photographic lens 8 perform focusing
operation based on the distance signal -
[0035] Fig. 4 is a diagram showing a concrete

20 configuration of the first signal processing

circuit 11 and the output circuit 15 in the AFIC
10. The second signal processing circuit 12 has
the same configuration of the circuit as that of
the first signal processing circuit 11.

25 [0036] As shown in Fig. 4, the first signal

processing circuit 11 inputs the short-range side

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signal Ii including the component of the ambient
light lo, which is output from the PSD 5, and
after removing the component of the ambient light
lo, outputs the short-range side signal Ii- The
5 current di + Io) / which is output from the near-

side terminal of the PSD 5, is input to the
negative input terminal of an operational
amplifier 20 in the first signal processing
circuit 11 through the PSDN terminal of the AFIC

10 10, The output terminal of the operational

amplifier 20 is connected to the base terminal of
a transistor 21; and the collector terminal of
the transistor 21 is connected to the base
terminal of the transistor 22. Connected to the

15 ■ collector terminal of the transistor 22 is . the
negative input terminal of the operational
amplifier 23; ' and connected to the collector
terminal is the cathode terminal of a compression
diode 24. Further, connected to the positive

20 input terminal of the operational amplifier 23 is

the cathode terminal of a compression diode 25;
and connected to the anode terminal of each of
the compression diodes 24 and 25 is a first
reference power supply 26.

25 [0037] Further, externally connected to the

CHF terminal of the AFIC 10 is a ambient light

17

removal capacitor 27. The ambient light removal
capacitor 27 is connected to the base terminal of
a ambient light removal transistor 28 in the
first signal processing circuit 11. The fixed
light removal capacitor 27 and the operational
amplifier 23 are connected to each other being
interposed by a switch 29, The CPU 1 controls
the ON/OFF operation of the switch 29. The
collector terminal of the fixed light removal
transistor 28 is connected to the negative input
terminal of the operational amplifier 20. The
emitter terminal of the transistor 28 is
connected to a resistance 30 of which another
terminal is grounded.

[0038] On the other hand, referring to Fig. 4,
the output circuit 15 is provided with an
integration capacitor 6, which is externally
connected to the CINT terminal of the AFIC 10.
The 'integration capacitor 6 is connected to the
output terminal of the arithmetic circuit 14
through a switch 60; and connected to a current
generator 63 through a switch 62; and further
grounded through a switch 64. These switches 60,
62 and 64 are controlled by the control signal
from the CPU 1. When the switch 62 is turned on,
the integration capacitor 6 is charged from the

18

current generator 63. On the other hand, when
the switch 64 is turned on, the integration
capacitor 6 is discharged.

[00391 Next, the operation of the distance

measuring device in accordance with the
embodiment will be described. Fig. 5 is a . timing
chart with respect .to the operation of the
distance-measuring device. When an operation of
the camera such as shutter release is made, the
distance measuring processing is started and the
AFIC 10 begins to be supplied with the power.
That is, a control signal is output from the CPU
1 to the driver 3, and the power supply voltage
is supplied from the driver 3 to the AFIC 10. In
the AFIC 10, receiving the power supply, the
integration capacitor 6 is charged. The
integration capacitor 6 is charged as a
dielectric absorption measure of the integration
capacitor 6.

[0040] Then,, after a predetermined time has

elapsed from the charge of • the integration
capacitor 6, a pulse PI is input to the AFIC . 10
from the CPU 1 as a control signal (CONT) . When
the pulse PI falls, the charged voltage of the
integration capacitor 6 is discharged, and the
ambient light removal capacitor 27 is charged

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FP03-0408-OC

swiftly. After that, a pulse P2 is input from
the CPU 1 as a control signal, and the swift
charge of the ambient light removal capacitor 27
is terminated.

5 [0O41] When a pulse P3 as a control signal is

input, corrective integration is carried out.
The corrective integration is carried out by
allowing a predetermined current to flow to the
integration capacitor 6 in a predetermined period
10 of time. Then, a pulse P4 as a control signal is

input, and the charged voltage of the integration
capacitor 6 is A/D converted and read by the CPU
1. ' ■

[0042] In the CPU 1, the capacity of the

15 integration capacitor 6 is calculated from the

A/D converted voltage value. By performing the
correction on the result of the distance
measuring calculation based on the actually
measured capacity, accuracy in the distance
20 measurement is improved.

[0043] Then, when a pulse P5 as a control

signal is input and the pulse P5 falls, the
integration capacitor 6 is discharged, and the
ambient light removal capacitor 27 is charged
25 swiftly. After that, a pulse P6 as a control

signal is input/ and the swift charge of the

20

ambient light removal capacitor 27 is terminated.
[0044] Thus, the distance measuring routine

is performed predetermined number of times. That
is, the IRED 4 projects the light onto the object
to be measured predetermined number of times at
predetermined intervals, and at every light
projection, the PSD 5 receives the reflected
light from the object to be measured and outputs
the near-side and long-range side signals. The
output ratio signal is calculated based on the
output near-side and long-range side signals .
The voltage corresponding to the output ratio
signal is repeatedly charged into the integration
capacitor 6. After completing the charge of
predetermined number of times, the charged
voltage of the integration capacitor 6 is A/D
converted and read by the CPU 1; and based on the
A/D converted value, the distance to .the object
to be measured is calculated. The distance
measuring operation may be performed in such
manner that a predetermined voltage is previously
charged in the integration capacitor 6, and a
voltage corresponding to the output ratio signal
is repeatedly discharged.

[0045] Next, the setting of the number of

times of the distance measuring routine in the

21

distance measuring device in accordance with the
embodiment will be described with reference to
the flow chart in Fig. 6. In this setting method^
an appropriate number of times of the distance
measuring routine for each product is determined
and stored in the EEPROM 2 prior to the shipment
from the plant. First of all, an object to be
measured with an infrared light reflectance of
36% is prepared at a short range alarm position
away from the distance measuring device (S102) ,
Using the object to be measured as an object, the
number of times "of the distance measuring routine
of the distance measuring device is set to a
temporal number of times (n-times) (5104);. and
the distance measuring operation is carried out
to obtain an AD signal. That is, a light beam is
projected onto the object to be measured from the
light projecting means {S106), the output ratio
signal is output from a calculation means (S108)
corresponding to the reflected light, which is
received by the light receiving means; thus
electric charge is accumulated in the integration
capacitor (SllO). The above operation is

repeated n-times at every pulse light (S112);
thus the electric charge of n-times is
accumulated in the integration capacitor as

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integration means. The voltage of the

integration capacitor, in which the electric
charge has been accumulated, is converted into an
AD signal by means of AD conversion means (S114) .
5 In this case, an appropriate number of times n is

selected in the following assumed difference
range; that is, in an individual product of which
capacity of the integration capacitor is the
smallest and the integrated current is the

10 largest, the integration capacitor is not

saturated'. Accordingly, the AD signal value
(referred to as ^^AFDATA") , which is obtained in
S114, is always resulted in a smaller value than
the AD signal value (referred to as ^^ADMAX") ,

15 which is obtained when the integration capacitor

is saturated.

[0046] The appropriate number of times of the

distance measuring routine (referred to as TI2)
for the individual distance measuring device is
20 calculated as the number of times in which n is

multiplied by the ratio between the ADMAX and the
AFDATA. • That is, ng is calculated using the
following mathematical expression (1) (S116):
n2=n-ADMAX/AFDATA... (1) .

In case where the integration capacitor is
discharged from the initial voltage state as the

23

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FP03~0408-

10

distance measuring routine is performed, riz is
calculated using the following mathematical
expression (2) :

n2=n-ADMAX/ ( ADMAX-AFDATA) ... (2 ) ;

provided that ADMAX in this case represents the
initial voltage (fully charged voltage), at the
time when the distance measuring routine is
initiated where' the AD signal value is
proportional to the voltage value of the
integration capacitor.
[0047] The obtained nz is set . a-s the number of

times of the distance measuring routine for the
distance measuring device (5118), and the setting
of the number of times is terminated.
[0048] The number of times of the distance

measuring routine and the AD signal value are
generally proportional to each other, and the
proportionality constant depends on the
characteristics of the circuits in the individual
distance measuring device and the distance of the
object. Accordingly, from the number of times of
n2 of the distance measuring routine, which is
obtained by the mathematical expression (1), the
AD signal value, when an object to be measured at
a short range alarm position is measured, is
resulted in a value that is almost the same as

24

20

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FP03-0408-

10

the ADMAX. In this case, the integration

capacitor is in the saturated state.

[0049] Fig. 7 is a timing chart for the

distance measuring device in accordance w.ith the
embodiment, in the case where a camera carries
out the distance measuring operation at the
closest distance capable of photographing. The
abscissa axis represents integration time; the
ordinate axis represents voltage of the
integration capacitor. As shown in Fig. 1, in an
individual product (distance measuring device 1)
of which capacity of the integration capacitor is
the smallest and the integration current is
largest, a small number of times of the distance
measuring routine A is set. Contrarily, in an
individual product (distance measuring device 3)
of which capacity of the integration capacitor is
the largest and the integration current is
smallest, a large number of times of the distance
measuring routine A is set up. Also,, in many
average individual products (distance measuring
device 2), an appropriate number of times of the
distance measuring routine B, which is between
the above two, is set up. In any of the distance
25 measuring devices, an appropriate number of times

of the distance measuring routine corresponding

25

15

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FP03-0408-

10

to the characteristics of the circuits is set up;
thereby electric charge is accumulated until the
voltage of the integration capacitor is
substantially saturated.

[0050] As described above, by setting the

voltage of the integration capacitor, which is
obtained at the short range alarm position, to
the maximum value, the range of distance from the
short range alarm position to the infinite
distance corresponds to the range from the
maximum voltage to the minimum voltage of the
integration capacitor as it is. Accordingly,
since the full range of the integration capacitor
voltage can be utilized, the resolution of the
15 distance measuring . device is increased; thus the

accuracy of the distance measurement can be
increased.

[0051] However, when the number of times of

the distance measuring routine is determined in
accordance with the . above-described adjustment
method, as shown in Fig. 7, the number of times,,
which is larger than the number of times of the
distance measuring routine in conventional
distance measuring device, is set up. That is,
the distance measuring time becomes longer than
that of the conventional distance measuring

20

25

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FP03-0408-

device. Therefore^ in the distance measuring
device that uses the above-described adjustment
method, in order to reduce the distance measuring
time, it is preferred that the capacity of the
5 integration capacitor is designed to be smaller

than that of the conventional one.

[0052] Further, the present invention is not

limited to the above-described embodiment, but
various modifications are possible. In the

10 above-described embodiment, the present invention

is applied to a camera with an • active distance
measuring system. In the case of camera in which
the active distance measuring system is used, the
present invention can be applied, for example, to
15 electronic still cameras as well as video cameras.

[0053] As described above, according to the

present invention, ' a distance measuring device
capable of increasing the accuracy of the
distance measurement without requiring any
complicated distance measuring processing.

20

27